Pirate 4x4 banner

Status
Not open for further replies.
1 - 20 of 96 Posts

·
Registered
Joined
·
1,779 Posts
Discussion Starter #1
The foil mentioned is out of heavy duty foil pans, the type you would receive 20 pounds of barbeque in for a picnic.

Is this a complete no-no? I understand that the following factors play into this situation:
galvanic corrosion
expansion/contraction rates
malleability of foil

Are there other factors to consider?

As for galvanic corrosion, I understand this is increased in the presence of a catalyst. Would gear oil be a corrosion limiter, since there are many diffs/transmissions with steel components inside aluminum cases?

I need to add that the shims are going between the pinion bearing and the pinion head. The bearing will not be able to rotate on the pinion shaft surface, so the shims will see no forces other than compression.

I would think the expansion contraction rate differences would be negligible, since we're only talking about .015" of foil.
 

·
Registered
Joined
·
1,779 Posts
Discussion Starter #3
Good point. I am asking because I used aluminum shims to initially setup my gears. I was planning to take out the aluminum shims and replace them with steel shims I have on the way through fastenal. I have the gears set up very well now, proper preload, backlash, pinion depth, etc.

This started me thinking, why not just leave the aluminum in there? I will probably end up taking out the foil shims and replacing them with steel ones, but I am just wondering why aluminum shims would be a bad idea.

A friend told me that he asked someone who sets up gears for a living about my desire to use aluminum shims. The guy's response was "they won't last, what a retard". I want to know why they won't last. And why he considers me a "retard" for pondering this. As far as I can tell it's not common knowledge (maybe it is, just in anecdotal form).
 

·
Registered
Joined
·
2,088 Posts
I would think that they would not last as well. There is some thrust load at all the bearings in your diff and I would think that over time the thickness of the shims will change.

Later,
Jason
 

·
Registered
Joined
·
862 Posts
I worked with a guy in a Toyota dealership that used a coke can to shim rod bearings when the crank was already turned once. It was his own motor, a Toyota 4AG, and it saw the rev limiter (7800 rpm) every day as long as he owned it!!
 

·
Registered
Joined
·
10,444 Posts
Cause they will deform over time..

Al used for baking is not exactly The toughest stuff in the world...
 

·
Premium Member
Joined
·
1,255 Posts
there are hundreds of different types of aluminum being used. The reason it probably wouldn't last would be the mallability (crushability)of the aluminum in a pie pan would not be strong enough to withstand the forces being put upon it. A different type of alloy might be able to hold up,but what's the point. "Just because" isn't a very good reason to go to this much trouble and expense to find out. Use the shims that have been tested already and known to work and move on. An experienced machinist would say this is retarded because he understands the metallurgy involved. It's like building your house out of shoebox cardboard instead of wood. Technically the cardboard is made from wood but it has very different properties. The cardboard would hold up for a while but would wind up falling down.
 

·
Registered
Joined
·
1,779 Posts
Discussion Starter #10 (Edited)
piratebuggy said:
It's like building your house out of shoebox cardboard instead of wood. Technically the cardboard is made from wood but it has very different properties. The cardboard would hold up for a while but would wind up falling down.
No, it's not like that at all. let's compare apples to apples.

It seems to be conventional wisdom that you can't use pie pan AL alloy for shims, but I haven't really heard compelling evidence either way. There seems to be so much anecdotal evidence floating around that everyone always cites, but nothing hard and fast.

I understand the pie plate AL is extra malleable, but I don't see how that matters in this case. The AL would have to practically liquefy and get squished completely out from between the pinion head and the pinion bearing to cause a problem. I can't imagine the pie plate AL shims I have doing that, but I could be dead wrong here.

I am no metalurgist, nor a machinist, but I do understand compression force. I would think using a tough plastic would actually work just as well in this scenario. The malleability of the material doesn't matter, as long as it's tough enough to not be forced out like an obese person's fat rolls from under spandex shorts.

Most of you are probably thinking, as some have already mentioned, "WHO CARES? Just use steel shims like everyone else."

I think using the tried and true steel shim stock would be a great idea, and would give me 100% confidence in the pinion depth, but I don't see why using some other material (pie plate AL in this case) would be a bad call. I'm just trying to learn.

All the AL has to do is maintain its present thickness, under the same pressure it's currently under. It's sandwiched in there very tightly, so it's not going to be galled, shredded, or worn down. It just has to maintain its thickness.

After I cut the shims out I sandwiched them together between two smooth steel plates and pressed them flat with my 12 ton press. I put lots of pressure on them and they didn't turn into liquid pancakes of aluminum, they just flattened and retained their shape. I can't imagine they would do anything different between the pinion bearing and the pinion head. :vader:
 

·
Registered
Joined
·
1,779 Posts
Discussion Starter #11 (Edited)
GearMan said:
:shaking: this has to be a fake ? you couldnt be serious could ya
No, I'm dead serious. Could you please tell me why this can't be done? I really want to know. Is it a secret or something? :vader:
 

·
Premium Member
Joined
·
9,603 Posts
hoohaa said:
After I cut the shims out I sandwiched them together between two smooth steel plates and pressed them flat with my 12 ton press. I put lots of pressure on them and they didn't turn into liquid pancakes of aluminum, they just flattened and retained their shape. I can't imagine they would do anything different between the pinion bearing and the pinion head. :vader:
Did you measure thickness before and after?
 

·
Premium Member
Joined
·
30,419 Posts
god I love rednecks I swear I do........of course it will work out just fine and your really expensive new gears that you just setup with your harbor freight mic will not mind a bit when the shim disenagrates....run it baby

oh ya be sure to post pics after you "break in" your new gears :flipoff2:
 

·
Registered
Joined
·
4,532 Posts
camo said:
god I love rednecks I swear I do........of course it will work out just fine and your really expensive new gears that you just setup with your harbor freight mic will not mind a bit when the shim disenagrates....run it baby

oh ya be sure to post pics after you "break in" your new gears :flipoff2:
thank you, sheesh all you nay sayers...of course it will work, I say run it. Please post pics once they're broke in like Camo said :D
 

·
Registered
Joined
·
10,444 Posts
You do realize that there are cyclic compression and extension forces on the pinion right??? It is not a matter of compress once and be done with it.
 

·
Registered
Joined
·
53 Posts
aluminum

prefab house builders tryed for years to use aluminum wire in houses.

what happeded you ask.

all the houses burned down.

reason.

aluminum will compress and deform more and more over time eaven 7075 T6.
the wire compresed out of the termanals and then started sparking and caused fires.

aluminum wire is used in power lines to save weight but only a specaly certified lineman can make an aluminum wire connection and they use an speical noncompresion connector.

it will compress and "migrate" out from shiming the bearings no matter what the grade or hardness.

if you give me some estmates on the pressure and surfice area i can give you and idea of how long it will take for the aluminum to do this. it might take so long that you can use pie pan aluminum to shim your pinyon and not have any illl efects.

Dustin Pares

PS steel does the same thing it just takes wwwwaaaaaaayyyyyyyyy longer
 

·
Registered
Joined
·
2,088 Posts
hoohaa said:
I understand the pie plate AL is extra malleable, but I don't see how that matters in this case. The AL would have to practically liquefy and get squished completely out from between the pinion head and the pinion bearing to cause a problem. I can't imagine the pie plate AL shims I have doing that, but I could be dead wrong here.
The thickness would not have to change that much in order to cause problems. There will be plenty of room for the shims to deform long before they would melt and flow as you are assumeing. You can buy shims at napa for dirt cheap. I would just get it done right.
 

·
Registered
Joined
·
1,779 Posts
Discussion Starter #19
Urban Wheeler said:
Did you measure thickness before and after?
I did, the individual sheet measured .005", and the stack measured just a smidgen under .015" after compressing with the press. There was no change after pressing.
 

·
Registered
Joined
·
1,779 Posts
Discussion Starter #20
Jason M said:
You do realize that there are cyclic compression and extension forces on the pinion right??? It is not a matter of compress once and be done with it.
Yes I do, but I'm not sure exactly what effect this will have on the shims. I understand that heat and stress will lead to compression and expansion, but I don't know if it really makes that much of a difference for a stack of shims .015" thick.

When I mentioned the initial compression I was referring to when I first pressed on the bearing. What I was trying to get at was that the pinion head and pinion bearing are never (let's hope :laughing:) going to separate far enough to let a shim rattle around loose. Yes there will be compression cycles, but not enough to loosen the shims significantly. I'm going to take a WILD guess here that the differences might be say, the compression cycles between a ton and two tons of pressure, just to throw a random number out there. (I have no clue how much pressure is actually there when the pinion nut is torqued, but I'm sure it would be easy for some of you to calculate) Sure, the compression does cycle, but even at the ebb of the cycle, the compression is still plenty to hold the shim in place. It would be interesting to know how much pressure is actually there between the pinion bearing and the pinion head. I forced the bearing onto the pinion with maybe 8 tons of force, then I torqued the pinion nut to 190 or so foot pounds of torque.

These are just my relatively uneducated guesses. It's "shadetree engineering" if you will. Don't hold back if I'm totally wrong.. My flame suit is on tight! (p.s. it's made of heavy duty foil :laughing:)

:vader:
 
1 - 20 of 96 Posts
Status
Not open for further replies.
Top